The present invention relates to hermetically sealed thermal shock resistant semiconductor devices and pertains particularly to hermetically sealed ultraviolet sensitive semiconductor chip and method of packaging the same.
Some semiconductor chips are responsive to light rays to either generate an output or change its response to a signal or input. For example, some programmable read only memory devices (PROMs) have been found to be eraseable by means of ultraviolet light. Such devices have gained wide acceptance in the industry because of the ease in programming thereof. These devices, however, must be hermetically sealed in order to ensure the reliability and functioning thereof and at the same time be packaged to be accessible by ultraviolet rays. Many approaches to the sealing of such devices have been proposed in the past.
The currently popular prior art approaches to the hermetically sealing of these read only memory devices are disclosed and discussed in the U.S. Pat. No. 3,924,246, issued Dec. 2, 1975 to Scherer, U.S. Pat. No. 3,217,379, issued Nov. 16, 1975 to Mesecke, and U.S. Pat. No. 3,281,606, issued Oct. 25, 1966 to Lueck. Another technique of packaging light responsive devices is shown in U.S. Pat. No. 3,482,198, issued Dec. 2, 1969 to Hopper, Jr., which is concerned with hermetic sealing but not thermal shock or ultraviolet transmission windows. Other packaging not concerned with hermetic sealing or shock resistance is shown in U.S. Pat. No. 2,773,925 to Rothlein et al. and U.S. Pat. No. 3,622,419 to London. These prior art approaches, however, still present numerous problems for which the present approach is devised to overcome.
One of such problems is that of obtaining a reasonable degree of thermal shock resistance, due to the bonding of a metallic mounting member to a ceramic packaging member. Such bonds when subjected to thermal shock are subjected to severe stresses as a result of the different expansion ratios between the window glass and the metallic members and between the ceramic and the metallic members. This is especially a problem where military specifications must be met. Other problems result from the high number of seals required for the metallic bond approach which result in more chances for leaks to develop within the system. This prior art approach was necessary because of the limitations of materials.
These prior art techniques are also more expensive in that they require special package structures and also require expensive metal fabrication and plating. The currently popular approach for example requires gold plating which is an expensive process.
These prior art approaches cannot take advantage of mass produced ceramic dual in line pin (CERDIP) packaging that is currently used for many semiconductor devices. The prior art approach was necessary because of the limitations of materials.
Accordingly, it is desirable that a new hermetically sealed thermal shock resistant package construction and method be devised for ultraviolet sensitive semiconductor devices.